The present invention relates generally to methods for supporting the back of a seated person, and to ergonomic chairs or seats and adjustable backrests configured to accomplish the method of the invention.
The human spinal column comprises a series of vertebral blocks extending from the occiput to the sacrum, or tailbone. The individual vertebra are united by longitudinal ligaments and by intervertebral discs disposed between laminae of cartilage. The spinal vertebra house the spinal cord and provide intervertebral outlets through which pass spinal nerves extending from the spinal cord.
Many experts believe that back pain or dysfunction will afflict 80% or more of the human population at some point in their lives. One presumed cause of back injury and dysfunction stems from poor posture. Poor posture can cause misalignment of the vertebra or degeneration of the intervertebral discs, which combined with compression of the spinal column from the weight of the upper body, can result in pinching and impingement of the spinal nerves. Pinching of the nerves can cause pain and impingement can interfere with the flow of neurological impulses, which can lead to various muscular disabilities. Moreover, even slight malalignments of the spinal column, though not permanent or injurious to the nerves, may cause muscles associated with the spine to fatigue, cramp, or spasm. In either case, the ailing individual feels pain.
A very large number of articles for sitting, hereafter collectively referred to as chairs, are available on the market, many of which purport to provide comfortable and ergonomically effective support and to encourage proper posture in order to prevent spine related problems such as those discussed above. However, the method of support employed by the pre-existing chairs does not provide the best biomechanical support for the spine. Also, such pre-existing chair designs are frequently complicated and expensive.
Furthermore, while many of these seats or chairs can be adjusted to suit a particular individual when seated in a single position, the chairs do not generally provide effective ergonomic support of the spine if the user moves. For example, the spatial relationship between the backrest and the seat of a chair in many pre-existing chair designs will change to a negative or less comfortable relationship with the user""s back when the user leans back in the seat or chair.
What is needed is a method of supporting the back of a seated person that provides back support that is superior to the support provided by preexisting methods implemented using preexisting chair designs. What is also needed is a chair and backrest configuration that allows the use of the improved method and that is adaptable for use in many kinds of seating.
Accordingly, the present invention comprises a method for supporting the back of a seated person. The method is intended to provide primary support to the back of a seated person at the junction between the lower thoracic vertebrae and the upper lumbar vertebrae and surrounding tissues. More specifically, the primary support is preferably provided to the spine in a target region generally around the 11th thoracic vertebrae and the 2nd lumbar vertebrae of a user of the chair, and more preferably between the 1st lumbar vertebrae and the 12th thoracic vertebrae, inclusive.
Support in the target region assists the spine of a seated person in maintaining a preferred posture, and also partially supports the weight of the spine above the lumbar region of the spine, which reduces the compressive forces experienced by the lumbar region of the spine. The method of the invention generally includes the following steps: (a) providing a backrest including a primary support region on the front surface of the backrest, and wherein the backrest is positionable to provide primary support to a target region of the spine of the seated person between the 2nd lumbar vertebrae and the 11th thoracic vertebrae, and (b) positioning the backrest by adjusting one or more dimensions of height, depth, and angle of the backrest so that the primary support region of the backrest contacts the target region of the spine between the 2nd lumbar vertebrae and the 11th thoracic vertebrae of a seated person, and more preferably between the 1st lumbar vertebrae and the 12th thoracic vertebrae.
In some embodiments, the method may further comprise the step (c) applying a selected amount of traction to the spine of the seated person as the backrest is deflected backwards as the seated person leans back. In such embodiments, the selected amount of traction is preferably between {fraction (1/16)} inch and xc2xc inch for each xc2xe inch to 1xc2xc inch of backwards deflection of said backrest, and more preferably xe2x85x9 inch for each 1 inch of backwards deflection of said backrest.
Preferably, In some embodiments of the method, the backrest does not provide support below the 2nd vertebrae.
Another aspect of the invention comprises a backrest that is configured to implement the method of the invention, and which may be incorporated into many other kinds of chairs or other kinds of seating, including but not limited to car seats, sofas, seats in public transportation vehicles, airlines, airport seats, public benches, and the like. The backrest is positionable to provide primary support to the spine in the region between the 1st lumbar vertebrae and the 12th thoracic vertebrae of a user of the chair, and in some embodiments may also support the region between the 11th thoracic vertebrae and the 2nd lumbar vertebrae, inclusive. The force applied by the primary support region of the backrest to the target region comprises a vector including both a vertical component and a horizontal component. The vertical vector partially supports the weight of the user above the lumbar region of the spine preferably reducing the compressive forces experienced by the lumbar region of the spine. In a preferred embodiment, the backrest is configured not to provide support directly to the lumbar region of the spine below the 2nd lumbar vertebrae. In other embodiments the backrest further includes a triangle-shaped protrusion for providing support to the thoracic region of the spine of the seated person. In the preferred embodiments, the primary support region is located proximate the bottom of the backrest.
A further aspect of the invention comprises a seat or chair configuration that is configured to accomplish the methods of the invention, including supporting the spine as described, and in some embodiments applying traction. Generally the chair includes a support structure, a seat operably connected to the support structure, and a backrest as previously described. In some embodiments, the backrest support structure comprises a support arm made of a sheet of resilient material having a length divided into four regions comprising a lower end section, a lower intermediate section, an upper intermediate section, and an upper end section. The depth of the seat may be adjustable by moving the lower end section of the support arm relative to a coupling affixed to the underside of the seat, and the height of the backrest may be adjustable along a length of an upper end section of the support arm. In alternate embodiments, the support arm may be coupled to the seat support structure, rather than to the underside of the seat.
In some embodiments the support structure supporting the seat includes one or more chair legs. In other embodiments, the support structure comprises a base including a mechanism for controlling and adjusting the height of the seat. Some embodiments may include a footrest. The footrest may comprise a body with a triangular cross section and an off center axis extending between the first end and the second ends. In still other embodiments, the backrest includes a protrusion for providing additional support for the thoracic portion of the spine.